1. Field of the Invention
This invention relates generally to systems and arrangements for balancing rotatory elements, and more particularly, to arrangements and methods of installing rotatory elements, such as the tire-wheel assemblies of vehicles, on to a spindle for determining the magnitude and location of a residual unbalance.
2. Description of the Related Art
It is well known to measure dynamic unbalance of tire-wheel assemblies in a single station balance. It is desired, however, to maintain a cycle time of 10 seconds or less, which corresponds to the typical cycle time of known multi-station balance systems. Within the cycle duration, a tire-wheel assembly that has been placed on a belt conveyor at the input side of the balance station is driven by the belt conveyor on to an elevator assembly that has incorporated into a vertically translatable platform thereof a chain conveyor and a centering mechanism. The chain conveyor and the centering arms cooperate within one another whereby the centering arms communicate with the outer periphery of the tire-wheel assembly and reposition same so that the central bore thereof is directly over a measuring spindle tooling. The elevator then lowers the tire-wheel assembly onto the balance measuring tooling and continues the downward motion to a predetermined lowered position whereby the elevator platform does not interfere with the rotation of the tire-wheel assembly on the balance tooling.
In the known arrangement, the balance tooling grips the central wheel bore of the tire-wheel assembly, which then is rotationally accelerated until a predetermined speed is attained. The predetermined speed is maintained during measurement of the residual unbalance, and then the tire-wheel assembly is decelerated and its rotation ultimately is stopped at a particular angular position corresponding to the location of the unbalance. At this point, as the elevator is raised, the underweight position on the vehicle side of the tire-wheel assembly is marked with an ink marker that is mounted to the elevator. A further marker arranged above the conveyor is moved into position such that when the elevator is in its upward position, the underweight spot on the curb side of the tire-wheel assembly is also marked. The tire-wheel assembly is then ready to be unloaded as the chain conveyor arrangement concurrently brings the next tire-wheel assembly into position for unbalance measurement.
A time-consuming and therefore critical portion of the cycle duration is the time required by the elevator to lower the tire-wheel assembly on to the balance spindle. Such lowering must be effected within a fraction of a second, but the rate of travel must be quite slow when the tire-wheel assembly communicates with the balancer tooling. If the tire-wheel assembly moves too quickly as it is installed on the balancer spindle, the bearings of the spindle may be damaged, or the tire-wheel assembly may bounce causing same not to be fully seated when the wheel bore is gripped.
In prior art arrangements, the elevator was smoothly accelerated and decelerated by operation of a crank that would drive a connecting link to the elevator, thereby creating a sinusoidal speed curve as the elevator travels between the maximum upper and lower positions. Such a known arrangement is quite adequate for a single tire-wheel assembly type wherein the height of the elevator above the spindle of the balancer is predetermined with respect to the axial location of the bore of the tire-wheel assembly. However, most vehicle assembly plant balancers operate on a variety of tire-wheel assemblies, each having a different distance from the vehicle side of the tire, which rests on the elevator, to the mounting surface of the wheel in the region of the central bore. Such a differential in the distances requires changes in the point along the travel of the elevator at which each such wheel engages the balancer tooling, such differences oftentimes being different from one another by several inches. There is a need, therefore, for an arrangement that determines this distance and operates the elevator whereby same is slowed as it approaches the precise point that the various tire-wheel assembly types will communicate with the tooling of the balancer system. Preferably, such an improved system advantageously would lower each tire-wheel assembly slowly only near the point of contact between the tire-wheel assembly and the balancer tooling and would accelerate to significantly higher speeds both, above and below the point of balance tooling engagement. In addition, there is a need for an elevator drive arrangement that, after completion of the unbalance measuring procedure, raises the tire-wheel assembly in a controlled manner whereby bouncing is prevented as the tire-wheel assembly is picked up off the balancer tooling and as it is stopped at the uppermost position for conveyance.
In addition to the foregoing, there is a need for an arrangement that can determine the distance required to be traveled by the elevator arrangement in order to achieve controlled gentle communication between the tire-wheel assembly and the balancer tooling.
It is, therefore, an object of this invention to provide an arrangement that controls the operation of an elevator that readily can be adapted to lower and raise a variety of types of tire-wheel assemblies to and from balancer tooling with a controlled deceleration as the assembly is installed on the balancer tooling.
It is another object of this invention to provide an elevator arrangement for lowering and raising a plurality of types of tire-wheel assemblies in a dynamic balancing machine.